The development of synaptic connections between peripheral sensory neurons and central interneurons will be examined using electrophysiological and dye injection techniques. It has been suggested that positional information guides the construction of the CNS of Acheta domesticus during ontogeny (Palka and Olberg, 1977). The theory proposes that the observed differences in synaptic connectivity which two classes of sensory cell make with a given follower interneuron are the result of their position on the sensory organ. I propose to first confirm the connectivity difference using electrophysiological techniques of higher resolution than previously available. I will then demonstrate precisely what aspect of synaptic function is different in the two classes of sensory neuron. The experiments are designed to demonstrate whether the apparent differences in strength of synaptic connection are due to differential probability of connection or differential transmitter release properties. The morphology of the presynaptic terminals will then be examined for evidence of a correlation between structure and connectivity. Finally a series of lesion experiments are designed to determine whether synaptic connections of one type of sensory cell depend on competitive interactions with the remaining class of sensory cells. The overall objective of the proposal is to determine, at the level of single neurons and single synapses, the neuronal processes which are controlled by positional information assigned early in the neurons life history. In other words, I will attempt to demonstrate the way in which positional information is "read out" by neurons which have received such information.